Research conducted within the Hypertension Division at the University of Michigan and other major institutions over the past 20 years have revealed that boderline hypertensives are characterized by excessive suppressed anger, submissivness, abnormalities in the control of hemodynamics, and greater elevations in blood pressure, heart rate, cardiac output and catecholamines in response to laboratory stressors. The majority of studies also show that the exaggerated response to stress is more pronounced when the stressors consist of difficult cognitive (mental stress) tasks. Although there is strong evidence that the exaggerated pressure responses to stress may proceed the development of hypertension, the great majority of data have been collected from homogeneous samples, usually consisting of white male, college student volunteers. As a result, there are no relevant completed studies comparing cardiovascular, pathophysiologic or hemodynamic correlates of behavioral factors in black versus white subjects. The goal is to investigate the relationships between mental stress, suppressed anger, and pathophysiology in young black and white adults with borderline (mild) hypertension. The fundamental aim of this proposal is to determine whether the abnormalities of the autonomic control of hemodynamics, personality traits, and membrane transport that are descriptive of young white hypertensives, are also present in young black borderline hypertensives. We expect to show that blacks and whites will exhibit similar pressure elevations to stress and sodium load; however, the pathophysiology will be markedly different for the ethnic groups. The other major aims are concerned with whether the exaggerated responses to mental stress in the laboratory are related to (a) elevated pressures in natural day-to-day settings, (b) target organ damage, (c) enhanced pressure elevations due to sodium level, and (d) characteristic membrane transport phenomena. A final aim of this proposal is to re-examine a subset of the sample after three years in order to learn about the stability of psychophysiologic interactions in borderline hypertension, and to draw inferences about pathophysiologic and hemodynamic profiles of black and white borderline hypertensives.